mtd: m25p80: Fix 4 byte addressing mode for Micron devices.

Submitted by Elie De Brauwer on Sept. 17, 2013, 5:48 p.m.


Message ID
State New, archived
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Commit Message

Elie De Brauwer Sept. 17, 2013, 5:48 p.m.
According to the datasheet for Micron n25q256a (N25Q256A13ESF40F) 4-byte
addressing mode should be entered as follows:

To enter or exit the 4-byte address mode, the WRITE ENABLE command
must be executed to set the write enable latch bit to 1. (Note: The
WRITE ENABLE command must NOT be executed on the N25Q256A83ESF40x and
N25Q256A83E1240x devices.) S# must be driven LOW. The effect of the
command is immediate; after the command has been executed, the write
enable latch bit is cleared to 0.

Micron's portable way to perform this for all types of Micron flash
is to first issue a write enable, then switch the addressing mode
followed by a write disable to avoid leaving the flash in a write-
able state.
 drivers/mtd/devices/m25p80.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

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diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 26b14f9..272d483 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -169,8 +169,16 @@  static inline int write_disable(struct m25p *flash)
 static inline int set_4byte(struct m25p *flash, u32 jedec_id, int enable)
 	switch (JEDEC_MFR(jedec_id)) {
 	case CFI_MFR_ST: /* Micron, actually */
+	{
+		int status;
+		write_enable(flash);
+		flash->command[0] = enable ? OPCODE_EN4B : OPCODE_EX4B;
+		status = spi_write(flash->spi, flash->command, 1);
+		write_disable(flash);
+		return status;
+	}
 	case 0xEF /* winbond */:
 		flash->command[0] = enable ? OPCODE_EN4B : OPCODE_EX4B;
 		return spi_write(flash->spi, flash->command, 1);